I think I would start by saying 4 Acc M4s are a seriously problematic aspect of US armor. While Shermans are threatening in A, their utterly, laughably, incredibly crap accuracy simply makes them a bad joke with low vet and in later Phases (2ID's M4A1s are basically wastes of points 90% of the time). A large part of the US's problems come down to how poor its AT is, and this is one of the larger aspects of that problem. A combination of generally inaccurate tools (that the 3AD shakes off unlike literally every other US div) and no easy front attack AP (is there even anything over 13 AP @ 1200m?) means you have to play ambush with things that suck at ambushing most of the time.
Make its staple be that 5 stack Sherman meme squad people always joke about. Granted, this is a highly dangerous thing to do because the capability of AT is drastically different in the low and high end. However, if we want to make a viably scary US armored division without resorting to things like good ATGs or high end mediums like the 3AD, then something else that can be dangerous needs to be considered. A single 5 card pack of extremely discounted Shermans in B would do a lot to make an armored division feel armored by levying those superior numbers to make up for the fact that none of them are going to actually hit anything with their first shots. I'm not sure just how drastically cheaper they should be, but something that makes them much more expendable (80 pts maybe?). If you really want to get fancy, make them Veteran too.
As for the rest of the tank tab, I would give a few cards of elite and veteran Stuarts (no cmders) in A, then the vet M4A1 76mms in B (FYI I think the M4A1 76mm should be 165). For C, give another two (three, four? IDK, the Axis armor divisions have obscene numbers of heavy tanks so it's kind of hard to give a parity) packs of the M4A1 spam except with one step higher vet and some three per pack M4A1 76mms at Elite. I have no clue why Eugen made all the 4AD's 76mm commanders as my knowledge of WWII TOE is limited, but the three per pack in C should not be commander to nerf the div's eco. The C game could also be augmented by a few 5 card M4A1 packs at even further discount (70 pt?) with the same B vet to satisfy the madmen that play TD. Throw in some normal M4A1 commands like the 2ID and 3AD have and that's the tank tab sorted.
Recon should be bog standard 25 pt Recon teams plus Phase A M3 Scouts with more being availible in later Phases as with M8s (preferably with vet because god are the rookies awful). This bit is fairly simple.
Infantry will be similar to the 12th SS in that you get trucks and HTs. I think an interesting flavor for the division might be to give the US some Panzergrens of its own, essentially LMG Rifles with a bazooka, call it Arm. Rifles + or something idk, putting them in B and C at like 4/6 availibility veteran in M3A1s. Phase A infantry should be Arm. Rifles leader (vet, jeep), Rifles (green, truck), and Arm. Rifles (green, M3 HT) with more availibility laden packs for alter phases (no vet increases) with some Engineers thrown in during B too (green, truck). This way you get a pretty bog standard infantry tab with no field punch in A, but still with AT options and trucks similar to the 12th. Then later into the game you get vet LMG equipped infantry but with bazooka tax so they have poorer cost effectiveness than the 3/4AD's. The only stars here would be the commanders and the Panzergren clones.
Support will be interesting. I think the usual 1/2/3 truck cargo works for this build. There should be M20 commands (availible in A) and some vet M8 Scotts in A to mix things up a bit (no 105mm Shermans). Add the throwaway flame squad no one uses and that's about it. Maybe if there is a support tab worthy Sherman variant that isn't a 105 that the US could use, throw that in for B and C as well for kicks.
Anti-tank should be the obligatory bazooka team (in A obviously, vet not required), M1 57mm (in jeeps please, HTs are trash for ATGs), plus some more veteran M1s in B and a single elite M5 76mm in C. Add a single pack of Veteran Wolverines in B (2 cards) with only one pack.
Anti-Air is a pretty standard fair, it doesn't really matter what you do. Might as well blatantly rob the 4AD's for all I care. You're going to have HTs, and that's about it.
To balance the fact that cheap Shermans are going to kind of mug light divisions without Stugs, the division should have no really notable arty in B, but still have the 3AD's M21s and infantry mortars in A. That way you get a division with really weak artillery in the mid-game but strong tank potential. Once C rolls around, they can have some 203mm OPs and Priests.
For air, give the deck P-51s like the 3AD but with vet ramp (2x rookie, 2x vet, 2x elite for A/B/C). Add some Thunderbolt bombers (the 165 pt ones) at veteran with some of the heavy 230 pt ones in C and the obligatory recon plane no ones uses and you have yourself a functional air tab. No rockets because idgaf.
Income will look somewhat like 75/140/125.
Slots would be:
Recon: 5
Infantry: 7
Tank: 7
Support: 4
Anti-Tank: 4
Anti-Air: 4
Artillery: 4
Air: 4
This essentially creates an Allied division specifically designed to be strong in B and have that lack of escalation that allows Axis armor decks to leverage them in C. Of note is the fact that there is no medium tank option in A. I thought about what makes amores decks so unfun to play against as infantry divisions and I concluded that it was HTs, mediums in A, meme SP HE bunkers, and arty a la Panzerwerfer. I took the effort to remove/gimp these aspects of this deck in an attempt to make it infantry div friendly. It's by no means clearly balanced, but can be tweaked to make this an interesting division, because this style isn't in the game yet. Bonus points is it gives Axis players a happy Sherman swarm div to farm, with limited arty making it a lot funner to play against AI using it.
It is something you have to play smart in A with as, while you don't have terrible income, you aren't wowing anyone with that unit comp or pt allotment either. This makes you have to play defensively against infantry divisions with no real way to dance with them besides Scotts and M21s, neither of which are that strong given price and what else you can get (cough, Stuff 42, cough). This division then gets its hey day in B with a larger income allowing you to start pushing out the assets necessary to bring out your Shermans and other gear. However your arty game does not get better until C, and even then, it's nothing special, which means infantry divisions can hold you down with some success (hopefully). Then in C, you ramp down and have to play second fiddle to divisions with stronger AT, but are still not helpless given you have a few good AT options (though inferior to the 3AD's).
There isn't a single thing over 9 AV to be seen, and nothing over 13 AP (except bazooka), but what the division lacks in the raw punch, it makes up for in tactical options with full squads of discount tanks.
Again, this division has no 1200m HE spacers, no heavy tanks, no mediums in A, no rocket arty, no Phase B arty in a Phase B income path, limited HTs, no 17 lber, no AT rockets, no Hellcat, etc.
